The present invention relates to an electronic parking brake (EPB), and more particularly, to an EPB which is capable of simplifying the configuration and additionally pressurizing a wheel disk during a parking brake operation.
In general, a brake system refers to a brake device which is used to not only decelerate or stop a vehicle in operation, but also maintain a parking state. Such a brake system typically uses a friction brake which converts kinetic energy into thermal energy. The friction brake performs a braking function while a brake pad pressurizes both sides of a wheel disk using hydraulic pressure, the wheel disk being rotated with a wheel. Since the hydraulic brake has a structure of strongly pushing the pad toward the disk using hydraulic pressure during a braking operation, the hydraulic brake inevitably has a complex structure including a master cylinder, a hydraulic line, and various devices. The master cylinder is operated through a booster for boosting a pedal force, and generates hydraulic pressure. The hydraulic line is connected toward a wheel cylinder, and the various devices control and assist the master cylinder and the hydraulic line. Furthermore, the hydraulic brake has a limitation in improving the reliability and stability of braking performance due to the complexity of the structure and the use of hydraulic pressure.
Recently, there has been used an EMB (Electro Mechanical Brake) which has a simpler structure and higher reliability in braking performance than the hydraulic brake. When an ECU (Electronic Control Unit) receiving electronic pedal information drives a motor to generate an axial moving force during a braking operation, a nut piston coupled to a motor is moved toward a brake pad, and the brake pad receiving the axial moving force of the nut piston is moved toward a wheel disk and generates a braking force by pressurizing the wheel disk.
However, since the EMB includes a decelerator and a non-self locking piston, the EMB has a complex structure. When various functions such as an EPB function are added, such a complex mechanism may become larger and heavier than a hydraulic caliper. Furthermore, as the entire structure becomes complex, the vehicle mountability may be degraded. Thus, there is a demand for a structure capable of solving such a problem.
The related art of the present invention is disclosed in Korean Patent Laid-open Publication No. 2012-0000838 published on Jan. 4, 2012 and entitled “Electronic parking brake device”.